IPC 620: Complete Guide to Wire Harness Acceptance Standards

Every wire harness that ships without a clear acceptance standard is a liability waiting to happen. A loose crimp in an automotive harness or a cold solder joint in medical equipment can cause recalls, downtime, or worse — safety failures.

IPC/WHMA-A-620 eliminates that ambiguity. It is the only industry-consensus standard that defines exactly what an acceptable cable and wire harness assembly looks like, from wire prep through final inspection. Whether you are building consumer electronics or flight-critical aerospace harnesses, this standard provides the visual and measurable criteria your team needs.

This guide breaks down the standard's structure, product classes, key inspection criteria, and certification options so you can implement IPC 620 effectively.

What Is IPC/WHMA-A-620?

IPC/WHMA-A-620 — formally titled "Requirements and Acceptance for Cable and Wire Harness Assemblies" — is a workmanship standard jointly developed by IPC (Association Connecting Electronics Industries) and WHMA (Wire Harness Manufacturers Association).

First published in 2002, the standard has gone through several revisions. The current version is Revision F (2025), which replaced Revision E (2022). Each revision incorporates industry feedback, new materials, and updated acceptance criteria.

"IPC 620 is not just a quality document — it is the shared language between OEMs and harness manufacturers. When both sides reference the same acceptance criteria, disputes over workmanship drop dramatically." — Industry Expert

What IPC 620 Covers

The standard spans 19 chapters addressing every major process in cable and wire harness production:

• Wire preparation — stripping, tinning, and handling
• Crimped terminations — stamped, formed, and machined contacts
• Soldering to terminals — cup, hook, bifurcated, and pierced terminals
• Insulation displacement connections (IDC)
• Ultrasonic welding and splicing
• Connector assembly — D-sub, circular, rectangular connectors
• Coaxial and biaxial cable termination
• Wire wrapping and point-to-point wiring
• Cable lacing, tie wrapping, and harnessing
• Shielding and grounding
• Marking and labeling
• Overmolding and potting
• Final assembly and inspection

What IPC 620 Does NOT Cover

The standard explicitly excludes:

• Wire cross-section (metallurgical) analysis criteria
• X-ray inspection rules
• PCB soldering — that falls under IPC J-STD-001
• Printed circuit board assembly acceptance — covered by IPC-A-610

The Three Product Classes Explained

IPC 620 defines three classes of product, each with increasingly strict acceptance criteria. The product class is specified by the customer or defined in the purchase order. If no class is specified, Class 2 is the default.

Class 1 — General Electronic Products

Class 1 applies to products where the primary requirement is basic function. Cosmetic imperfections and minor workmanship deviations are acceptable as long as the assembly works.

Typical applications:

• Consumer electronics (toys, simple appliances)
• Disposable or short-life products
• Non-critical lighting and hobby equipment

Acceptance philosophy: If it functions, it passes. Visual imperfections that do not affect electrical performance are generally acceptable.

Class 2 — Dedicated Service Electronic Products

Class 2 covers products requiring continued performance and extended life. Uninterrupted service is desired but not critical — meaning brief outages are tolerable.

Typical applications:

• Communications equipment
• Industrial controls and instrumentation
• Business machines and commercial HVAC
• Automotive non-safety systems

Acceptance philosophy: Higher cosmetic and workmanship standards than Class 1. Minor deviations are acceptable if they do not compromise reliability over the product's expected service life.

Class 3 — High-Performance Electronic Products

Class 3 is the strictest tier. It applies to products where continued high performance or performance-on-demand is critical. Equipment failure cannot be tolerated, and the end-use environment may be extreme.

Typical applications:

• Life support and implantable medical devices
• Flight-critical aerospace and defense systems
• Military weapons systems
• Nuclear facility controls
• Deep-sea and space exploration equipment

Acceptance philosophy: Near-zero tolerance for defects. Every crimp, solder joint, and wire termination must meet the highest visual and measurable standards.

Class Comparison Table

Criteria	Class 1	Class 2	Class 3
Defect tolerance	Functional defects only	Minor cosmetic allowed	Near-zero tolerance
Crimp bellmouth	Not required	Recommended	Mandatory — perfect flare
Damaged strands	Acceptable if functional	Limited percentage	Zero severed strands
Solder wetting	Adequate coverage	Good wetting angle	Full wetting, specific angles
Insulation clearance	Basic requirements	Moderate tolerances	Exact positioning in window
Inspection magnification	Minimal	Standard (1.5–3x)	Enhanced (up to 10x)
Documentation	Basic	Detailed	Full traceability
Default if unspecified	No	Yes	No

Key Inspection Criteria

Crimped Terminations

Crimping is the most common termination method in wire harness production. IPC 620 provides detailed acceptance criteria with over 700 full-color photographs showing acceptable and defect conditions.

Critical crimp requirements:

1. Wire type — Only stranded wire may be crimped. Solid wire crimping is prohibited.
2. No pre-tinning — Never solder (tin) wire strands before crimping. Solder cracks under pressure and creates unreliable connections.
3. Bellmouth — The flared opening at the crimp barrel entrance. Class 3 requires a visible, symmetrical bellmouth to prevent wire chafing. Class 2 recommends it. Class 1 does not require it.
4. Crimp height — Must fall within the terminal manufacturer's specified tolerances. Cross-section analysis may be required for Class 3 qualification.
5. Insulation support — The insulation crimp must grip the wire insulation without cutting into it. The conductor must not be visible between the insulation grip and the wire crimp.
6. Strand damage — Class 3 tolerates zero severed or broken strands. Class 2 allows a limited percentage based on total strand count.

"The number one crimp defect we see in audits is pre-tinned wire. Engineers tin wire out of habit from soldering work, but tinned strands in a crimp barrel will cold-flow over time and loosen the connection. IPC 620 explicitly prohibits it for good reason." — Quality Assurance Specialist

Soldered Terminations

For terminals that require soldering — cup terminals, hook terminals, bifurcated terminals — IPC 620 aligns its requirements with IPC J-STD-001:

• Wetting — Solder must flow smoothly onto both the wire and terminal surface. Cold joints (grainy, dull texture) are defects at all class levels.
• Fill — Cup terminals must be filled to a minimum level depending on class. Class 3 requires 75% minimum fill.
• Flux residue — Must not interfere with subsequent operations or long-term reliability. Clean per the flux manufacturer's recommendations.
• Heat damage — Insulation discoloration from soldering heat must not extend beyond specified limits from the terminal.

Wire Preparation

Proper wire prep is the foundation of every good termination:

• Strip length — Must match the terminal manufacturer's specification ±tolerance per class
• Strand damage during stripping — Automated cut-and-strip machinery is strongly recommended for Class 3 to prevent strand nicking
• Insulation damage — Cuts, nicks, or burns on wire insulation adjacent to the strip area are defects in Class 2 and 3

Cable Lacing and Tie Wrapping

IPC 620 covers both traditional lacing (using waxed cord or flat tape) and modern cable ties:

• Lacing tension — Must be firm enough to hold the bundle shape but not crush or deform wires
• Cable tie tails — Must be trimmed flush. Sharp edges that could damage adjacent wires are defects in all classes
• Spacing — Lacing spots or ties must be evenly spaced to maintain consistent bundle diameter

Inspection Magnification Requirements

The standard specifies minimum magnification based on the feature being inspected:

Wire Diameter (AWG)	Wire Diameter (mm)	Required Magnification
14 AWG and larger	> 1.63 mm	Unaided eye
14–22 AWG	1.63–0.64 mm	1.5x to 3x
22–26 AWG	0.64–0.40 mm	3x to 7.5x
26 AWG and smaller	< 0.40 mm	7.5x to 10x

Lighting must be a minimum of 1000 lux at the inspection surface for all classes.

IPC 620 Certification and Training

Certification Levels

IPC offers a structured certification program:

CIS — Certified IPC Specialist

• For operators and inspectors on the production floor
• 3–4 day course covering all 19 chapters
• Written exam with hands-on practical assessment
• Must be renewed every 2 years

CIT — Certified IPC Trainer

• For in-house quality engineers who train CIS candidates
• More intensive curriculum with teaching methodology
• Authorized to issue CIS certifications within their organization

MIT — Master IPC Trainer

• Highest level — trains the trainers
• Authorized by IPC-accredited training centers

Is Certification Worth It?

For manufacturers serving automotive, aerospace, medical, or defense markets — yes, certification is often a contractual requirement. Major OEMs like Boeing, Lockheed Martin, and Honeywell require IPC 620 certification as a condition of doing business.

Even without contractual requirements, certification provides measurable benefits:

• Reduced rework rates — trained operators catch defects before they reach inspection
• Standardized accept/reject decisions — eliminates subjective quality disputes
• Audit readiness — ISO and customer auditors recognize IPC certification
• Cross-team communication — everyone speaks the same quality language

How to Implement IPC 620 in Your Facility

Step 1: Determine Your Product Class

Work with your customer to establish the required product class. If the customer does not specify, Class 2 applies by default. Document the class in your work instructions and inspection procedures.

Step 2: Train Your Team

Send at least one quality engineer for CIT certification so they can train production staff in-house. All operators and inspectors working on harness assemblies should achieve CIS certification.

Step 3: Build Workmanship Standards

Create visual workmanship standards using photographs of your actual products. Show examples of acceptable, process indicator, and defect conditions for each termination type your facility produces.

Step 4: Set Up Inspection Stations

Equip inspection stations with:

• Calibrated magnification tools per the table above
• Minimum 1000 lux lighting
• Go/no-go crimp height gauges
• Pull-test equipment for crimp and solder validation
• Reference copies of IPC 620 with color photographs

Step 5: Establish Process Controls

For Class 3 production, implement:

• First-article inspection on every new setup
• In-process crimp height monitoring (SPC recommended)
• Pull-test sampling per lot
• Final visual inspection of 100% of terminations
• Full traceability from wire lot to finished harness

IPC 620 vs Related Standards

Standard	Scope	Relationship to IPC 620
IPC/WHMA-A-620	Cable & wire harness assemblies	This standard
IPC-A-610	PCB assembly acceptance	Companion — covers board-level assembly
IPC J-STD-001	Soldered electrical connections	Referenced — IPC 620 aligns soldering criteria
IPC-A-600	Bare PCB acceptability	Separate — PCB fabrication quality
UL 486A-486B	Wire connector/terminal standards	Safety certification — complementary
SAE AS7928	Wire harness (aerospace)	Industry-specific — overlaps with Class 3

Frequently Asked Questions

What is the current version of IPC 620?

The latest version is IPC/WHMA-A-620F, released in 2025. It replaces Revision E (2022) and incorporates updated acceptance criteria, new connector types, and improved alignment with IPC J-STD-001.

What happens if no product class is specified?

Class 2 is the default. If your customer's purchase order does not specify a class, all acceptance criteria default to Class 2 requirements.

Can I use IPC 620 for PCB assembly inspection?

No. IPC 620 covers cable and wire harness assemblies only. For PCB assembly acceptance criteria, use IPC-A-610. For soldered connections on PCBs, reference IPC J-STD-001.

How often must IPC 620 certification be renewed?

CIS certification must be renewed every 2 years. CIT certification follows a similar cycle. Renewal typically involves a refresher course and re-examination.

Does IPC 620 apply to automotive wire harnesses?

Yes. Many automotive Tier 1 and Tier 2 suppliers use IPC 620 Class 2 or Class 3 as their acceptance standard, particularly for safety-critical harnesses (airbag, ABS, steering). Some OEMs have additional requirements layered on top of IPC 620.

What is the difference between IPC 620 and IPC-A-610?

IPC-A-610 covers acceptance of printed circuit board assemblies (components soldered to PCBs). IPC 620 covers cable, wire, and harness assemblies (crimped, soldered, or mechanically attached terminations). They are companion standards — many facilities need both.

Conclusion

IPC/WHMA-A-620 is the definitive standard for cable and wire harness quality. Understanding its three product classes, mastering the visual acceptance criteria, and investing in team certification are the foundations of a reliable harness production operation.

Start by confirming your product class with your customer. Train your inspectors to CIS level. Build visual workmanship references specific to your products. Then enforce the standard consistently — because quality is not what you inspect at the end but what you build into every termination.

For related inspection and design tools, explore our DFM design rules reference for PCB trace and via specifications, or use our trace width calculator to verify your designs meet current-carrying requirements.

References

• IPC/WHMA-A-620 Overview — Wikipedia
• IPC 620 Standard Details — Wiring Harness News
• IPC Training & Certification Programs — EPTAC
• IPC 620 Crimped Termination Requirements — SuperEngineer
• A-620 Cable Testing Standard Summary — Cirris